The present invention relates generally to antenna apparatus used to transduce radio frequency signals, such as the radio frequency signals generated by, or received at, a mobile terminal operable in a cellular, or other radio, communication system. More particularly, the present invention relates to an antenna assembly, and an associated method, which utilizes a counter antenna element together with an active antenna element. The counter antenna element operates to reduce the frequency about which the active antenna element is resonant without necessitating a corresponding increase in the length of the active antenna element. The antenna assembly is thereby able to be of reduced lengthwise dimensions relative to conventional antennas operable about a resonant frequency.
A communication system permits the communication of information between a sending station and a receiving station by way of a communication channel. The sending station is operable to generate a communication signal of characteristics permitting its communication upon the communication channel. And, the receiving station is operable to recover the informational content of the communication signal.
A radio communication system is a communication system in which the communication channel upon which the communication signal is communicated is formed of a radio channel. The radio channel is defined upon a portion of the electromagnetic spectrum. Because a wireline connection is not required to form the communication channel between the sending and receiving stations, communications are possible when such a wireline connection between the sending and receiving stations would be impractical. Improved communication mobility is also possible through use of a radio communication system.
A sending station forming a portion of a radio communication system includes a transmitter for modulating information upon a carrier wave of a carrier frequency within the range of frequencies which defines, at least in part, the communication channel. Through such a process, a baseband signal of which the information is formed is converted into a radio frequency signal of desired frequency characteristics.
The transmitter typically includes one or more up-mixing stages at which the baseband information is up-converted in frequency to be of the selected radio frequency. The mixing stages include mixer circuits coupled to receive the information and an up-mixing signal with which the information is to be multiplied, or otherwise combined, to form an up-converted signal. When multiple mixing stages are utilized, an if (intermediate frequency) signal is formed at a first, or first series of, mixer stages. A radio frequency signal is formed at the final mixing stage.
A receiving station operable to receive a radio-frequency communication signal transmitted thereto upon a radio communication channel, analogously, converts the radio frequency signal to a baseband level. One or more down-conversion stages down-converts the radio frequency signal to a baseband level.
A cellular communication system is exemplary of a radio communication system. Cellular communication systems, constructed according to various cellular communication standards, have been installed throughout significant portions of the world. A subscriber to a cellular communication system is able to communicate therein by way of a mobile terminal when the mobile terminal is positioned within an area encompassed by the communication system. Telephonic communication of both voice and nonvoice information is permitted by way of such communication systems. The mobile terminal is formed of transceiver circuitry and includes both a sending station and a receiving station.
A mobile terminal operable in a cellular communication system, or other communication system providing for two-way communications, includes both a transmitter and a receiver to permit the sending of, and reception of, communication signals thereat.
Both the transmitter and the receiver are connected, typically, to an antenna transducer. The antenna transducer transduces radio frequency, electrical signals generated by the transmitter into electromagnetic form for communication upon the communication channel. And, the antenna transducer transduces electromagnetic signals communicated upon the communication channel and received at the receiver, into electrical form to permit receiver operation to be performed upon the resultant, electrical signal. A single antenna transducer is typically utilized for both the transmitter and receiver of a mobile terminal, or other two-way communication device, through utilization of a filter duplexer when communications are effectuated pursuant to a frequency division multiplexing scheme having separate transmit and receive passbands.
Advancements in integrated circuit, and other, technologies have permitted reduction in the physical dimensions of electronic circuits, such as the circuits of which the receiver and transmitter of a mobile terminal are formed. Many mobile terminals operable in cellular communication systems, for instance, are contained in housings which permit the mobile terminals, so-formed, to be carried by a user and stored, for instance, when not in use, in a shirt pocket, or the like, of the user.
Antenna transducers, forming essential portions of most mobile terminals, however, have generally not exhibited a corresponding decrease in their physical dimensions. Such antenna transducers are, conventionally, of lengths related to the wavelengths of the signals to be transduced by the antenna transducer. As a result, while other portions of the mobile terminal are of increasingly smaller dimensions, the antenna transducers of the mobile terminals form increasingly large proportions of the resultant packages of which the mobile terminals are formed.
If a manner could be provided by which to reduce the lengthwise dimension of the antenna transducer while still ensuring operation of the antenna transducer to transduce signals of a selected range of wave lengths, a radio circuit including such an antenna transducer could be of reduced physical dimensions.
It is in light of this background information related to antenna apparatus that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides antenna apparatus, and an associated method, in which a counter antenna element is positioned at a selected distance from an active antenna element. The counter antenna element operates to permit the frequency about which the active antenna element is resonant to be reduced without necessitating an increase in the length of the active antenna element. The separation distance separating the counter antenna element and the active antenna element is determinative of the reduction in the resonant frequency about which the active antenna element is operable to transduce send and receive signals. By reducing the frequency about which the antenna transducer is resonant without requiring alteration of the lengthwise dimension of the active antenna element, increased miniaturization of the communication device of which the antenna element forms a portion is possible.
In one aspect of the present invention, an antenna assembly is provided for a mobile terminal operable in a cellular, or other radio, communication system. The antenna assembly includes an active antenna element positioned to extend in a forward direction and an antenna counter element positioned proximate thereto and extending in a reverse direction. The antenna counter element is spaced apart from the active antenna element by a selected distance. The selected distance by which the antenna counter element is spaced apart from the active antenna element is determinative of the alteration in frequency about which the active antenna element is resonant. By causing appropriate reduction in the frequency at which the active antenna element is resonant, a reduction in the lengthwise dimension of an active antenna element, operable over a selected range of frequencies, relative to conventional antenna elements, is possible.
In such an implementation, the mobile terminal is provided with an antenna assembly capable of transducing communication signals, either transmit signals or receive signals, about a resonant frequency at which the active antenna element of the assembly is resonant.
In one implementation, the active antenna element is mounted upon a substrate at which at least portions of the radio circuitry of the mobile terminal are disposed. The active antenna element is positioned to extend in a forward direction, i.e., a dorsal side portion of the active antenna element is connected to a ground part of the radio circuitry of the mobile terminal. And, the active antenna element is also connected to an rf (radio frequency) part of the radio circuitry of the mobile terminal. The antenna counter element is also mounted upon the substrate and is positioned to extend in a reverse direction, i.e., the antenna counter element is connected at a distal side portion thereof to the ground part of the radio circuitry of the mobile terminal. In isolation, the active antenna exhibits resonance about a first resonant frequency. Positioning of the antenna counter element at a selected distance therefrom offsets the resonant frequency at which the active antenna element is resonant to a forward, offset resonant frequency. Because of the inverse relationship between frequency and wavelength, and because the active antenna element is of a lengthwise dimension dependent upon the wavelength of signals to be transduced thereat, an offset of the frequency at which the active antenna element is resonant, caused by the antenna counter element, permits an active antenna element of reduced lengthwise dimensions, relative to conventional active elements, to be utilized at the mobile terminal. In an implementation in which the mobile terminal forms a dual-mode device, separate active antenna elements, each of reduced lengthwise dimensions relative to their conventional counterparts, are employed at the mobile terminal.
In a further implementation, the antenna assembly includes an active antenna element positioned to extend in the forward direction, i.e., the active antenna element is connected at a dorsal side portion thereof to the ground part of the radio circuitry of the mobile terminal. The active antenna element is further coupled to the rf part of the radio circuitry. An antenna counter element is positioned proximate to the active antenna element, at a selected spaced distance therefrom, and positioned to extend in a reverse direction, i.e., the antenna counter element is connected at a distal side portion thereof to the ground part of the radio circuitry. A third antenna element is also utilized, spaced-apart from the antenna counter element, and positioned to extend in a forward direction, i.e., the third antenna element is connected at a dorsal side portion thereof to the ground part of the radio circuitry. The third antenna element is operable to alter the frequency characteristics of the resultant antenna assembly. By positioning the third antenna element in proximity to the antenna counter element and, in turn, the active antenna element, the resultant antenna assembly is resonant about a single resonant frequency rather than at two or more separate resonances.
In another implementation, the active antenna element and the antenna counter element are positioned in tandem and maintained in a spaced-apart relationship by the selected separation distance. The resultant antenna assembly is translatably coupled to a substrate to permit translation of the active antenna element together with the antenna counter element, thereby to be positionable at least alternately in an xe2x80x9cupxe2x80x9d position and in a xe2x80x9cdownxe2x80x9d position.
In these and other aspects, therefore, an antenna assembly, and an associated method, is provided for radio circuitry operable to communicate radio signals. The radio circuitry includes a ground part and an rf (radio frequency) part. A first antenna element has a dorsal side portion and a distal side portion. The first antenna element is connected at a ground-part-connection location of the dorsal side portion thereof to the ground part of the radio circuitry. The first antenna element is connected to the rf part of the radio circuitry at an rf-part-connection location. The rf-part-connection location is spaced apart from the ground-part-connection location. The first antenna element, in isolation, is resonant about a first resonant frequency. A second antenna element also has a dorsal side portion and a distal side portion. The second antenna element is spaced apart from the first antenna element by a first selected distance. The second antenna element is connected at a ground-part-connection location of the distal side portion thereof to the ground part of the radio circuitry. Positioning of the second antenna element at the selected distance from the first antenna element offsets the first resonant frequency at which the first antenna element is, in isolation, resonant, thereby to be resonant at a first offset frequency.
A more complete appreciation of the present invention and the scope thereof can be obtained from the accompanying drawings, which are briefly summarized below, the following detail description of the presently-preferred embodiments of the present invention, and the appended claims.